patch 8.2.2351: Vim9: error msg for "throw" in function called with "silent!"

Problem:    Vim9: error message for "throw" in function that was called with
            "silent!".
Solution:   Do not throw the exception when not caught or displayed.
            (closes #7672)

src/testdir/test_vim9_script.vim

@@ -564,6 +564,19 @@ def Test_throw_skipped()
   endif
 enddef
 
+def Test_nocatch_throw_silenced()
+  var lines =<< trim END
+    vim9script
+    def Func()
+      throw 'error'
+    enddef
+    silent! Func()
+  END
+  writefile(lines, 'XthrowSilenced')
+  source XthrowSilenced
+  delete('XthrowSilenced')
+enddef
+
 def DeletedFunc(): list<any>
   return ['delete me']
 enddef

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2351,
 /**/
     2350,
 /**/

src/vim9execute.c

@@ -2605,6 +2605,17 @@ call_def_function(
 		break;
 
 	    case ISN_THROW:
+		if (ectx.ec_trystack.ga_len == 0 && trylevel == 0
+								&& emsg_silent)
+		{
+		    // throwing an exception while using "silent!" causes the
+		    // function to abort but not display an error.
+		    tv = STACK_TV_BOT(-1);
+		    clear_tv(tv);
+		    tv->v_type = VAR_NUMBER;
+		    tv->vval.v_number = 0;
+		    goto done;
+		}
 		--ectx.ec_stack.ga_len;
 		tv = STACK_TV_BOT(0);
 		if (tv->vval.v_string == NULL